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can: c_can: Speed up tx buffer invalidation

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It's suffcient to kill the TXIE bit in the message control register
even if the documentation of C and D CAN says that it's not allowed to
do that while MSGVAL is set. Reality tells a different story and this
change gives us another 2% of CPU back for not waiting on I/O.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Alexander Stein <alexander.stein@systec-electronic.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
This commit is contained in:
Thomas Gleixner 2014-04-11 08:13:22 +00:00 committed by Marc Kleine-Budde
parent 35bdafb576
commit 939415973f
2 changed files with 40 additions and 15 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

54
drivers/net/can/c_can/c_can.c
View File

@ -276,11 +276,34 @@ static inline void c_can_object_put(struct net_device *dev, int iface,
c_can_obj_update(dev, iface, cmd | IF_COMM_WR, obj);
}
/*
* Note: According to documentation clearing TXIE while MSGVAL is set
* is not allowed, but works nicely on C/DCAN. And that lowers the I/O
* load significantly.
*/
static void c_can_inval_tx_object(struct net_device *dev, int iface, int obj)
{
struct c_can_priv *priv = netdev_priv(dev);
priv->write_reg(priv, C_CAN_IFACE(MSGCTRL_REG, iface), 0);
c_can_object_put(dev, iface, obj, IF_COMM_INVAL);
}
static void c_can_inval_msg_object(struct net_device *dev, int iface, int obj)
{
struct c_can_priv *priv = netdev_priv(dev);
priv->write_reg(priv, C_CAN_IFACE(ARB1_REG, iface), 0);
priv->write_reg(priv, C_CAN_IFACE(ARB2_REG, iface), 0);
c_can_inval_tx_object(dev, iface, obj);
}
static void c_can_setup_tx_object(struct net_device *dev, int iface,
struct can_frame *frame, int obj)
struct can_frame *frame, int idx)
{
struct c_can_priv *priv = netdev_priv(dev);
u16 ctrl = IF_MCONT_TX | frame->can_dlc;
bool rtr = frame->can_id & CAN_RTR_FLAG;
u32 arb = IF_ARB_MSGVAL;
int i;
@ -291,9 +314,20 @@ static void c_can_setup_tx_object(struct net_device *dev, int iface,
arb |= (frame->can_id & CAN_SFF_MASK) << 18;
}
if (!(frame->can_id & CAN_RTR_FLAG))
if (!rtr)
arb |= IF_ARB_TRANSMIT;
/*
* If we change the DIR bit, we need to invalidate the buffer
* first, i.e. clear the MSGVAL flag in the arbiter.
*/
if (rtr != (bool)test_bit(idx, &priv->tx_dir)) {
u32 obj = idx + C_CAN_MSG_OBJ_TX_FIRST;
c_can_inval_msg_object(dev, iface, obj);
change_bit(idx, &priv->tx_dir);
}
priv->write_reg(priv, C_CAN_IFACE(ARB1_REG, iface), arb);
priv->write_reg(priv, C_CAN_IFACE(ARB2_REG, iface), arb >> 16);
@ -401,17 +435,6 @@ static void c_can_setup_receive_object(struct net_device *dev, int iface,
c_can_object_put(dev, iface, obj, IF_COMM_RCV_SETUP);
}
static void c_can_inval_msg_object(struct net_device *dev, int iface, int obj)
{
struct c_can_priv *priv = netdev_priv(dev);
priv->write_reg(priv, C_CAN_IFACE(ARB1_REG, iface), 0);
priv->write_reg(priv, C_CAN_IFACE(ARB2_REG, iface), 0);
priv->write_reg(priv, C_CAN_IFACE(MSGCTRL_REG, iface), 0);
c_can_object_put(dev, iface, obj, IF_COMM_INVAL);
}
static netdev_tx_t c_can_start_xmit(struct sk_buff *skb,
struct net_device *dev)
{
@ -436,7 +459,7 @@ static netdev_tx_t c_can_start_xmit(struct sk_buff *skb,
* can_put_echo_skb(). We must do this before we enable
* transmit as we might race against do_tx().
*/
c_can_setup_tx_object(dev, IF_TX, frame, obj);
c_can_setup_tx_object(dev, IF_TX, frame, idx);
priv->dlc[idx] = frame->can_dlc;
can_put_echo_skb(skb, dev, idx);
@ -563,6 +586,7 @@ static int c_can_chip_config(struct net_device *dev)
/* Clear all internal status */
atomic_set(&priv->tx_active, 0);
priv->rxmasked = 0;
priv->tx_dir = 0;
/* set bittiming params */
return c_can_set_bittiming(dev);
@ -654,7 +678,7 @@ static void c_can_do_tx(struct net_device *dev)
idx--;
pend &= ~(1 << idx);
obj = idx + C_CAN_MSG_OBJ_TX_FIRST;
c_can_inval_msg_object(dev, IF_RX, obj);
c_can_inval_tx_object(dev, IF_RX, obj);
can_get_echo_skb(dev, idx);
bytes += priv->dlc[idx];
pkts++;

1
drivers/net/can/c_can/c_can.h
View File

@ -174,6 +174,7 @@ struct c_can_priv {
struct net_device *dev;
struct device *device;
atomic_t tx_active;
unsigned long tx_dir;
int last_status;
u16 (*read_reg) (struct c_can_priv *priv, enum reg index);
void (*write_reg) (struct c_can_priv *priv, enum reg index, u16 val);